Even Kale May Contain Toxic PFAS

Kale is considered one of the healthiest foods available in U.S. grocery stores. But not even these leafy superfoods are safe from contamination by toxic forever chemicals, according to a new study.

A small pilot study found that seven of eight kale samples purchased from different grocery stores across the U.S. were contaminated with poly- and perfluoroalkyl substances (PFAS).

This class of more than 12,000 chemicals has been linked to serious health outcomes, including liver and thyroid disease, certain cancers, suppressed immune function, and birth defects. These so-called “forever chemicals” accumulate in the environment and human bodies and are extremely challenging, if not impossible, to remove once they’re there.

According to the Food and Drug Administration (FDA), “most foods not grown or produced in specific geographic areas with known PFAS contamination do not have detectable levels of PFAS.” In a 2020 study, the FDA found that 97% of more than 700 fresh and processed food samples, including kale, were PFAS-free.

Researchers from the Alliance for Natural Health, a nonprofit organization that advocates for alternative medicine, sought to validate that claim. The group tested a bunch of conventional kale and organic kale from retail grocery stores in four states—New York, Georgia, Pennsylvania, and Arizona.

The pilot study is too small to draw robust conclusions, but it raises questions about how much PFAS has seeped into the U.S. food system.

“We intended this not to be the final say, but to spur additional research and, more importantly, a stronger response from the federal government to protect Americans from these dangerous chemicals,” Robert Verkerk, PhD, executive and scientific director at the Alliance for Natural Health USA, told Verywell.

How Did PFAS Wind Up in Kale?

PFAS are known for their water-, heat-, and grease-resistant properties. These chemicals are commonly used in waterproof clothing, nonstick cookware, cosmetics, fire-fighting foams, and more. When these goods are manufactured and disposed of in landfills, PFAS can leach into soil and waterways.

The toxins are now ubiquitous. A report from the U.S. Geological Survey estimates that at least 45% of U.S. tap water is contaminated with one or more PFAS. They’re found in the bloodstream of virtually every person in the U.S.

The researchers decided to test for PFAS in kale “because it’s viewed as one of the healthiest options at the store,” Verkerk said.

“Frankly, we were also expecting to find no detectable residues in the organic kale—so you can imagine our surprise when we found all four samples of organic kale, and three out of four of conventionally grown kale were contaminated,” Verkerk said.

Farmers sometimes use biosolids—the sludge leftover when wastewater is treated—to fertilize their crops. These biosolids can be contaminated with high levels of PFAS, which make their way into plants as they grow.

It’s not clear whether the kale samples tested were grown in sludge or watered with contaminated water. It’s also possible that the kale picked up PFAS from the plastic packaging they were sold in, according to Tasha Stoiber, PhD, a senior scientist specializing in PFAS at the Environmental Working Group who was not involved with the study.

Verkerk said that the group did not test the packaging for PFAS, but factors like polluted irrigation must be at play because the unpackaged kale was also tainted.

Can You Avoid PFAS in Food?

Just how concerned should people be about the PFAS in their food? “That’s exactly the question that we should be asking. And I think it’s difficult to answer because we don’t have a lot of data on food,” Stoiber said.

Other food sources may contain even more PFAS. One serving of freshwater fish, for instance, can contain the same amount of PFAS as a month’s supply of drinking water.

Microwave popcorn bags, fast food containers, pizza boxes, and other grease- and water-resistant food packaging is often full of PFAS. Some states have banned the use of PFAS in food packaging, but there are no federal regulations yet.

“Our recommendation is to eat fresh whole foods, like kale, because packaged foods are the ones that can have really high levels of PFAS from that grease-proof paper,” Stoiber said.

She said the recommendation holds true despite the new study findings. But there’s a lot that scientists still don’t know about the pervasiveness of PFAS in produce and the food system at large.  

“I myself have a lot of questions, and I’d love to see 50 kale samples or a hundred kale samples from around the U.S. I think the data here really just scratches the surface—it would be good to see it see more so we can understand more in general about the contamination from our food,” Stoiber said.

In the meantime, there’s no obvious way to clean PFAS from food. One study found that cooking fish in large amounts of water or oil for a long time and then discarding the cooking liquid could remove some PFAS. But there isn’t much data to indicate that cooking or washing methods will work on vegetables.

“That’s because the contamination, especially if it comes from irrigation water, isn’t just on the outside of the plant,” Verkerk said. “The issue isn’t PFAS-contaminated kale per se, it’s more that we likely live in a PFAS-contaminated world that poses a public health threat.”

The best way to try and tackle the PFAS problem, he said, is for federal regulators to ban the entire class of chemicals and work together to scrub them from the environment.

“This is a ticking time bomb for both human health and environmental impacts,” Verkerk said.